This invention relates generally to gaseous discharge lamps of the low, medium and high pressure type, and more particularly to a system for effecting cold ignition of fluorescent lamps by momentarily applying across the electrodes thereof an ignition voltage higher than the normal operating voltage derived from a standard a-c supply (i.e., 120 or 220 volts).
In fluorescent lamps of the type in present day use, the electrodes must be preheated before ignition is initiated. In most cases, an ignition voltage whose magnitude is greater than the normal operating voltage is applied to the electrodes, the ignition voltage being generated by an induction circuit.
With conventional ignition arrangements, there is a measurable time lag between the actuation of the switch and the actual ignition of the lamp. Moreover, in many instances, several trial or false ignitions may precede the actual lamp ignition, this giving rise to disturbing flicker effects. Until such time as full ignition occurs, the full light output of the lamp is not available, this being inconvenient and annoying to the user of the lamp.
Attempts have heretofore been made to overcome delayed ignition and its attendant drawbacks. But these attempts have failed in a practical way to realize ignition of a fluorescent or other gas discharge lamp almost immediately upon closing the operating switch.
Thus British Pat. No. 512,778 discloses an ignition system in which a current-limiting or choke coil for the lamp is tapped to form an autotransformer providing a high ignition voltage. But this arrangement is not feasible, for the resultant ignition current is of such intensity that it is difficult to cope with, especially in large installations. Also, the heavy ignition current seriously deteriorates the hot cathodes and blackens the lamp in a relatively short time. Hence, the life span of such lamps is relatively short, and the resultant maintenance and replacement costs as well as shut-downs render this approach to rapid ignition uneconomical.